003xxx.mp3, etc., where xxx = any text. Commands are
sent from the micro to the RX pin at 9600 baud, 8, 1, N,
True.

It’s not necessary to connect the module’s TX pin,
unless you want to get “file finished” signals. Serial
commands from the user manual are shown in Figure 7.
The same format is used for all commands; numbers are
in hex notation. There’s an Arduino sketch at

BOLD RED numbers are the “constants.” All
commands start with 7E,FF; all commands have a central
00; and all commands end in EF. In this example, 06 =
total number of values in the command string, ignoring
initial 7E and terminating EF. Use 0F = operator to play a
specified folder# and file#; 01 = folder 01; 03 = sound
file 003xxx.mp3. Note that 06 (number of command values)
stays 06 unless you use operator 21 to specify multiple files
to played sequentially.

Always remember that the MP3 module has its own
slave microcontroller. On power-up, it should be given a half
second to boot up before the master controller sends any
commands to it. Initialize it with the reset command 0C,
followed by a half second pause; then use command 09 to
specify utilizing the micro SD card. Include another pause
before sending any play commands.

Once a sound file starts playing, the MP3’s slave
controller will play it all the way to the end unless stopped
by the master controller. A new play command will
interrupt the current song.

Finally, real B- 9 fans will recall that the B- 9 robot could
shoot high voltage sparks (lightning) from his claws. What
if we could have it all — a robot project combining sound
The MP3 player module outputs stereo sound, which is
dumbed down to mono within this small speaker amp. If
you need stereo for a project, then — by all means — use
two speakers, whether nice amplified computer speakers or
two of these mini speaker balls. Obviously, most music
MP3s come in stereo format for better sound.

Alternatively, you could record two different sides of a
conversation on the L/R channels to recreate this epic
showdown between B- 9 and his brother, Robby:
https://www.youtube.com/watch?v=ov6svgh8sSQ.
You could certainly fit lots of B- 9 robot quips on a 32 GB
micro SD card! For starters, visit www.soundboard.com
/sb/Lost_in_space_robot which has many memorable
sound bytes.

SERVO 10.2017 11

Figure 8.

That’s all for now, earth creatures.

As always, please send your emails and questions to
roboto@servomagazine.com. We’ll see you next time. SV